Tag: posterior fossa decompression

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Duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression for pediatric Chiari malformation type 1 with syrinx

Acta Neurochirurgica (2024) 166:70

In posterior fossa decompression for pediatric Chiari malformation type 1 (CM-1), duraplasty methods using various dural substitutes have been reported to improve surgical outcomes and minimize postoperative complications. To obtain sufficient posterior fossa decompression without cerebrospinal fluid-related complications, we developed a novel duraplasty technique using a combination of a pedicled dural flap and collagen matrix. The objective of this study was to describe the operative nuances of duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression for pediatric CM-1.

Methods We reviewed the clinical and radiographic records of 11 consecutive pediatric patients who underwent posterior fossa decompression with duraplasty using a combination of a pedicled dural flap and collagen matrix followed by expansile cranioplasty for CM-1. The largest area of the syrinx and the size of the posterior fossa were calculated.

Results The maximum syrinx area was reduced by a mean of 68.5% ± 27.3% from preoperatively to postoperatively. Four patients (36.4%) had near-complete syrinx resolution (> 90%, grade III reduction), five (45.5%) had 50% to 90% reduction (grade II), and two (18.2%) had < 50% reduction (grade I). The posterior fossa area in the midsagittal section increased by 8.9% from preoperatively to postoperatively. There were no postoperative complications, including cerebrospinal fluid leakage, pseudomeningocele formation, or infection.

Conclusion Duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression is a promising safe and effective surgical technique for pediatric CM-1 with syrinx.

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Cerebrospinal fluid area and syringogenesis in Chiari malformation type I

J Neurosurg 134:825–830, 2021

Syringogenesis in Chiari malformation type I (CM-I) is thought to occur secondary to impaction of the cerebellar tonsils within the foramen magnum (FM). However, the correlation between the CSF area and syringogenesis has yet to be elucidated. The authors sought to determine whether the diminution in subarachnoid space is associated with syringogenesis. Further, the authors sought to determine if syrinx resolution was associated with the degree of expansion of subarachnoid spaces after surgery.

METHODS The authors performed a retrospective review of all patients undergoing posterior fossa decompression for CM-I from 2004 to 2016 at the University of Virginia Health System. The subarachnoid spaces at the FM and at the level of the most severe stenosis were measured before and after surgery by manual delineation of the canal and neural tissue area on MRI and verified through automated CSF intensity measurements. Imaging and clinical outcomes were then compared.

RESULTS Of 68 patients, 26 had a syrinx at presentation. Syrinx patients had significantly less subarachnoid space at the FM (13% vs 19%, p = 0.0070) compared to those without syrinx. Following matching based on degree of tonsillar herniation and age, the subarachnoid space was significantly smaller in patients with a syrinx (12% vs 19%, p = 0.0015). Syrinx resolution was associated with an increase in patients’ subarachnoid space after surgery compared with those patients without resolution (23% vs 10%, p = 0.0323).

CONCLUSIONS Syrinx development in CM-I patients is correlated with the degree to which the subarachnoid CSF spaces are diminished at the cranial outlet. Successful syrinx reduction is associated with the degree to which the subarachnoid spaces are increased following surgery.

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Chiari I malformation: surgical technique, indications and limits

Acta Neurochir (2018) 160:213–217

Chiari malformation type I (CM-I) is a rare disease characterised by herniation of cerebellar tonsils below the foramen magnum with associated anomalies of posterior fossa. We describe here the surgical technique, indications and limits of surgical treatment.

Method The authors describe the surgical technique, including: posterior fossa decompression, opening of the foramen of Magendie and duraplasty in case of CM-I.

Conclusions Posterior fossa decompression plus duraplasty is a safe and effective procedure for patients with CM-I malformation.

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Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging

J Neurosurg 126:1934–1940, 2017

A subset of patients with Chiari I malformation demonstrate patent subarachnoid spaces around the cerebellum, indicating that reduced posterior fossa volume alone does not account for tonsillar descent. The authors distinguish two subsets of Chiari I malformation patients based on the degree of “posterior fossa crowdedness” on MRI.

METHODS Two of the coauthors independently reviewed the preoperative MR images of 49 patients with Chiari I malformation and categorized the posterior fossa as “spacious” or “crowded.” Volumetric analysis of posterior fossa structures was then performed using open-source DICOM software. The preoperative clinical and imaging features of the two groups were compared.

RESULTS The posterior fossae of 25 patients were classified as spacious and 20 as crowded by both readers; 4 were incongruent. The volumes of the posterior fossa compartment, posterior fossa tissue, and hindbrain (posterior fossa tissue including herniated tonsils) were statistically similar between the patients with spacious and crowed subtypes (p = 0.33, p = 0.17, p = 0.20, respectively). However, patients in the spacious and crowded subtypes demonstrated significant differences in the ratios of posterior fossa tissue to compartment volumes as well as hindbrain to compartment volumes (p = 0.001 and p = 0.0004, respectively). The average age at surgery was 29.2 ± 19.3 years (mean ± SD) and 21.9 ± 14.9 years for spacious and crowded subtypes, respectively (p = 0.08). Syringomyelia was more prevalent in the crowded subtype (50% vs 28%, p = 0.11).

CONCLUSIONS The authors’ study identifies two subtypes of Chiari I malformation, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation.

 

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Minimally invasive subpial tonsillectomy for Chiari I decompression

minimally-invasive-subpial-tonsillectomy-for-chiari-i-decompression

Acta Neurochir (2016) 158:1807–1811

A number of different surgical techniques have been used through the years to address Chiari I malformation (CMI).

Methods This article describes how we surgically manage CMI at two high-volume centers. We call the technique the minimally invasive subpial tonsillectomy (MIST). The technique consists of a minimalistic dissection and craniectomy with a short, linear durotomy for the subpial tonsillar resection. The dura is closed without the use of a duraplasty.

Conclusions We describe our current methods of surgery for CMI.

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Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation

Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation

J Neurosurg 122:1068–1075, 2015

The authors completed a prospective, institutional review board–approved study using intraoperative MRI (iMRI) in patients undergoing posterior fossa decompression (PFD) for Chiari I malformation. The purpose of the study was to examine the utility of iMRI in determining when an adequate decompression had been performed.

Methods Patients with symptomatic Chiari I malformations with imaging findings of obstruction of the CSF space at the foramen magnum, with or without syringomyelia, were considered candidates for surgery. All patients underwent complete T1, T2, and cine MRI studies in the supine position preoperatively as a baseline. After the patient was placed prone with the neck flexed in position for surgery, iMRI was performed. The patient then underwent a bone decompression of the foramen magnum and arch of C-1, and the MRI was repeated. If obstruction was still present, then in a stepwise fashion the patient underwent dural splitting, duraplasty, and coagulation of the tonsils, with an iMRI study performed after each step guiding the decision to proceed further.

Results Eighteen patients underwent PFD for Chiari I malformations between November 2011 and February 2013; 15 prone preincision iMRIs were performed. Fourteen of these patients (93%) demonstrated significant improvement of CSF flow through the foramen magnum dorsal to the tonsils with positioning only. This improvement was so notable that changes in CSF flow as a result of the bone decompression were difficult to discern.

Conclusions The authors observed significant CSF flow changes when simply positioning the patient for surgery. These results put into question intraoperative flow assessments that suggest adequate decompression by PFD, whether by iMRI or intraoperative ultrasound. The use of intraoperative imaging during PFD for Chiari I malformation, whether by ultrasound or iMRI, is limited by CSF flow dynamics across the foramen magnum that change significantly when the patient is positioned for surgery.

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Posterior fossa volume increase after surgery for Chiari malformation Type I: a quantitative assessment using magnetic resonance imaging and correlations with the treatment response

J Neurosurg 115:647–658, 2011.DOI: 10.3171/2010.11.JNS102148

The aim of this paper was to measure the posterior fossa (PF) volume increase resulting from a givensized occipital craniectomy in Chiari malformation Type I surgery and to analyze its correlations with the PF size and the treatment response, with the perspective of tailoring the amount of bone removal to the patient-specific PF dimensions.

Methods. Between January 2005 and June 2006, 11 adult patients with symptomatic Chiari malformation Type I underwent a standardized PF decompression. A prospective evaluation with clinical examination, functional grading, and MR imaging measurement protocols was performed pre- and postoperatively. A method is reported for the measurement of PF volume (PFV) after surgery. The degree of PFV increase was compared with the preoperative size of the PF and with the clinical outcome.

Results. All 11 patients improved postoperatively, with complete and partial recovery in 4 and 7 patients, respectively. No postoperative complication occurred after a mean follow-up period of 45 months. The mean relative increase in PFV accounted for 10% (range 1.5%–19.7%) of the initial PFV; the increase was greater in cases in which the PF was small (r = -0.52, p = 0.09) and the basiocciput was short (r = -0.37, p = 0.2). A statistically significant positive correlation was found between the degree of PFV increase and the treatment response (p = 0.014); complete recovery was observed with a PFV increase of 15% and partial recovery with an increase of 7%.

Conclusions. The treatment response is significantly influenced by the degree of PFV increase, which is dependent on the size of the PF and the extent of the craniectomy, suggesting that the optimal patient-specific PFV increase could be predicted on the basis of preoperative MR imaging and enhancing the perspective that the craniectomy size could be tailored to the individual PFV.

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